Voltage-controlled ring oscillators



Feb. 21, 1956 K. E. FORSBERG 2,735,939

VOLTAGE-CONTROLLED RING OSCILLATORS Filed Nov. 5, 1952 Tl T1" l6. 0

ATTORNEY United States Patent 2,735,939 VOLTAGE-CONTROLLED RING OSCILLATORS Kenneth E. Forsberg,.Great Neck, N. Y., assignor toRaytheon Manufacturing Company, Newton, Mass a corporation of Delaware Application November 3, 1952, Serial No. 318,439 8 Claims. (Cl. 250-36) This invention relates to oscillator circuits whose periods of oscillation are linearly controlled by two ormore control voltages to determine the oscillatory period.

In many applications involving pulse techniques and counter operations, it is desirable to have a train of pulses having precisely determined, variable pulse duration and repetition rate. In many cases, it is also desirable that such variations be in accord withthe variation of one or more control voltages. By the present invention, such an oscillator is made from at least two monostable multivibrators, with the plate of the normally nonconducting tube of one of the multivibrators coupledto the plate of the normally conducting tube of the other multivibrator with controlling voltages coupled to the grid of the normally nonconducting tube of each multivibrator, so that one voltage controls the duration of the output pulse and the other voltage determines the interval between. the pulses. In thecase of a train of pulses ofrelativelylong duration with respect to. the interval between pulses, the voltage applied to such a'circuit for determining the. duration of the pulses may be considered as a coarse control, in that it controls'the larger parameter, and the voltage controlling the interval between pulses as a fine control, in that it controls the smaller interval of. time. Such a circuit permits frequency control over a wide range of frequencies. Ranges of from five to one are easily obtainable. Such a circuit is inexpensive to build and maintainias it only requires capacitors and resistors, in addi-v tion to the tubes and power sources, and needs no relatively expensive inductances. For this and other reasons, the circuit is particularly useful for the automatic controlof low frequency oscillations, particularly square waves. More than two voltages may be used to determine the pulse repetition rate and'duration of the waveform by theuse of more than two multivibrators inthe circuit of this invention.

Other and further advantages of this invention will be apparent as the description thereof'progresses, reference being had to the accompanying drawings wherein:

Fig. l is a schematic diagram of the. circuit of one embodiment of the invention;

Fig. 2a is a time diagram of the wave form appearing at the output of the first multivibrator;

Fig. 2b is a time diagram of the waveform appearing at the output of the second multivibrator;

Fig. 2c is a time diagram of the wave form appearing at the output of the oscillator; and

Fig. 3 is a schematic diagram of a circuit embodying the invention with more than two multivibrators and controlling voltages.

In Fig. 1, the reference numeral represents .the normally nonconducting tube of the first multivibrator. This tube has a plate 11, a grid 12, and a cathode 13. The plate 11 is connected to a source 14 of positive potential through a resistor 15. The grid 12. is connected to an input terminal 16. The cathode 13 of the first tube 10 is connected to the cathode 17 of a second tube 18 and to the negative terminal of the source 14 of positive potential through a common resistor 24?. The plate 21 of the tube 18iis connected to the source 14through a resistor 22; The grid 23 of the tube 18 is coupled to'the plate 11015 the tube10 through a capacitor 24, and is connected to the source'14 of'positive. potential through a resistor 25. Theplate 21"of'the tube 18 is' coupled to the plate 26 of a third tube"27"through a capacitor 28. The plate 26" is' connected" to the source 14 of'positive' potential through a resistor'30. The grid 31 of the tube 27 is con nected to'input terminal 32. The cathode'33 is connected to the'cathode 34of a fourth tube'3sand to'a' common load'resistor 36. Theplate 26 of the tube 27 iscoupled tothe-grid'37 of the fourth tube'35 through a capacitor 38; The grid'37'of'the tube 35 is also connected to the source'1'4 of'positive potentialthrougharesistor 40; The plate 41 is coupled to theplate 11 of'the tube'10 through a capacitor 42. The plate 41 is also connected to the source 14 of positive potential through a resistor43 andto an output terminal 44.

In operation, the tubes'lll'and 18 and their associated components constitute a monostablecathodercoupledmultivibrator producing a square wave output, such as the Wave form 50 in Fig. 2a, at the plate 21 of the tube 18. The duration ii of 'these'positive pulses'is determined by the voltage Ei applied at the input terminal 16. This voltage maybe the-combination ofa direct current bias and a triggering pulse. It may'also be an-adjustable biasing voltage that-is'made to vary in' responsetosome condition that it is desired to have control theduration and frequency of the pulses at the output of this oscillator. This wave form 50 -is' appliedtostheplatex26zof the tube 27 0f the "second monostable multivibrator through the capacitor 28. The second multivibrator; consisting of'tub'es 27 and 35 and their associated components, produces a i square wave output, such as wave form 51 shown in the graph of Fig, 2b. A control-voltage- E2 is'applied'tothe input terminal 32 which determines the durationiofi' these: posi tive pulses' r2. This'wave form51'appearing attthe plate 41- of the* tube: 35 .-is coupled back-'through1capacitor 42 to the plate 11' ofsthe tube -10. Theresult'is'a wave form 52 appearing at the output terminal44: Itwill be seen that the leading edge 53 of the output :wave'form '52 occurs coincident with the leading edger54 of 'the :wave form 50, and.the duration of the pulse-is-determined by the pulse duration t1. Theleading; edge 56' of :wavezform 51 occurs coincidentwith the trailingedge SS ofiwavezform 52, and thistimeis-coincident with the-:termination of the pulse duration n of waveform 50. The pulse duration tz'deter mines-the. time-at which theoscillatorrecycles. This is accomplished by having the" multivibrator" comprising tubes 10 and 18"trigger themultivib'rator comprising tubes 27 and 35-atthe end of' the first multivibrators unstable period. In turn, thesecond multivibrator triggers the first at theend of-the second-multivibratoris unstable peri- 0d; The oscillatory period of each multivibrator'is related to the applied controlling voltage ,E1 or E2'as follows:

T1=KiE1 and where K1 and.K2. are factors dependent upon the-fixed parameters of. the. respective multivibrators. The period of theresultant wave form is This principle can be extended to any number of multi: vibrators, as shown in Fig. 3, where the first two multie vibrators comprisingtubesillfl; 118, 127, and1135- are connected'in the same manner as the multivibratorsicorne prisingtubes 10; 18, 27; and35, shown in Fig. l and de scribed above. The components of these multivibrators have been given the same reference. numerals as in Fig. .1 but are precededb'y thenumeral l. Additionalmultivibrators, -such-as those comprising tubes'1'60'and 161;

i have beeneadded. Theadditional multivibratorsare'connected in a manner similar to those shown in Fig. 1. The plate 162 of the tube 160 is connected to the source 114 of positive potential through a resistor 163. The grid 164 is connected to an input terminal 165. The cathode 166 is connected to the cathode 167 of the tube 161 and returned to the negative terminal of the source 114 through a resistor 168. The plate 162 is coupled to the grid 169 of the tube 161 through a capacitor 170. The grid 169 is also connected to the source of positive potential 114 through a resistor 171. The plate 172 of the tube 161 is connected to the source of positive potential 114 through a resistor 173. The plate 162 of the tube 160 is coupled to the plate 141 of the tube 135 through a capacitor 175. The plate 172 of the tube 161 is coupled to the plate 110 of the tube 118 through a capacitor 174 and is also connected to an output terminal 144.

In operation, the multivibrators comprising the tubes 127 and 135 trigger the multivibrator comprising tubes 160 and 161 at the end of the second multivibrators unstable period. In turn, the third multivibrator triggers the first through the capacitor 174 at the end of the third multivibrators unstable period. Recycling occurs when the first multivibrator triggers the second multivibrator through the capacitor 128 at the end of the first mnltivibrators unstable period. As before, the oscillatory period T of each multivibrator is related to the applied controlling voltage E by the factor K. Thus, the overall period of a change in such a ring of multivibrators will be The result is a ring oscillator having an output wave form, the repetition rate and pulse duration of which is dependent upon the values of any desired number of voltages each of which may, in turn, be made dependent upon some other condition.

This invention is not limited to the particular details of construction, materials and processes described, as many equivalents will suggest themselves to those skilled in the art. It is, accordingly, desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

l. A voltage-controlled oscillator comprising a plurality of multivibrators arranged in a ring-oscillator circuit, each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator except the first to the plate of the normally conducting device of the preceding multivibrator and the plate of the normally nonconducting device of the first multivibrator to the plate of the normally conducting device of the last multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

2. A voltage-controlled oscillator comprising a plurality of voltage-sensitive multivibrators arranged in a ring-oscillator circuit, each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator except the first to the plate of the normally conducting device of the preceding multivibrator and the plate of the normally nonconducting device of the first multivibrator to the plate of the normally conducting device of the last multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

3. A voltage-controlled oscillator comprising a plurality of monostable multivibrators arranged in a ring-oscillator circuit, each having a normally conducting and a normally nonconducting electron discharge device having a +KNEN plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator except the first to the plate of the normally conducting device of the preceding multivibrator and the plate of the normally nonconducting device of the first multivibrator to the plate of the normally conducting device of the last multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivribrator to linearly control the pulse duration and repetition rate of the output.

4. A voltage-controlled oscillator comprising a plurality of cathode-coupled multivibrators arranged in a ringoscillator circuit, each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator except the first to the plate of the normally conducting device of the preceding multivibrator and the plate of the normally nonconducting device of the first multivibrator to the plate of the normally conducting device of the last multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

5. A voltage-controlled oscillator comprising a pair of multivibrators each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode capacitive means to couple the plate of the normally nonconducting device of each multivibrator to the plate of the normally conducting device of the other multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

6. A voltage-controlled oscillator comprising a pair of voltage-sensitive multivibrators each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator to the plate of the normally conducting device of the other multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

7. A voltage-controlled oscillator comprising a pair of monostable multivibrators each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator to the plate of the normally conducting device of the other multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

8. A voltage-controlled oscillator comprising a pair of cathode-coupled multivibrators each having a normally conducting and a normally nonconducting electron discharge device having a plate, a grid and a cathode, capacitive means to couple the plate of the normally nonconducting device of each multivibrator to the plate of the normally conducting device of the other multivibrator, means to apply a controlling voltage to the grid of the normally nonconducting device of each multivibrator to linearly control the pulse duration and repetition rate of the output.

References Cited in the file of this patent UNITED STATES PATENTS 2,402,916 Schroeder June 25, 1946 2,492,736 Custin Dec. 27, 1949 2,494,353 Newman Jan. 10, 1950 2,612,560 Rea Sept. 30, 1952 

